What is the significance of the term "bar" in music notation and how does it impact the structure and rhythm of a musical composition?

In music notation, a "bar" is a segment of time that divides music into equal parts. It is marked by vertical lines on the staff. Bars help organize the music into manageable sections and establish the rhythm of the composition. The number of beats in each bar, as indicated by the time signature, determines the overall structure and flow of the music.